I have a Image and I want to paint on top of it some square. But I keep getting undefined function on getContext('2d'). I must add that the var img is an image which is already loaded on the page, I'm trying to interpret it as a canvas since I am using another script which lets to select areas on the image and if I use a canvas the script will not work. So in the case where I can not interpret a image as a canvas what would you suggest?
Js function
function drawInput(dx1,dy1,dx2,dy2) {
var img = document.getElementById('home:tempImg');
var canvas = img;
console.log(canvas);
var context = canvas.getContext('2d');
var imageObj = new Image();
imageObj.onload = function() {
context.drawImage(imageObj, dx1, dy1,dx2-dx1,dy2-dy1);
};
imageObj.src = 'images/selected.png';
}
HTML
<h:body>
<h:form onsubmit="#{getComponents.getAllComponents()}" id="home">
<div>
<p:graphicImage id="tempImg" rendered="true" value="#{imageView.selectedImg}">
</p:graphicImage>
</div>
</h:form>
</h:body>
<script type="text/javascript">
var myJSONStr ='{ "area" : #{areaInputView.areaListString}}';
console.log(myJSONStr);
var json = JSON.parse(myJSONStr);
//console.log(json.area[1].x1);
for(var i=0;myJSONStr.length >i ; i++) {
console.log(json.area[i].x1, json.area[i].y1, json.area[i].x2, json.area[i].y2);
drawInput(json.area[i].x1, json.area[i].y1, json.area[i].x2, json.area[i].y2);
};
</script>
</html>
By leveraging custom JS 'classes' (of the type app.Image in this case), we can build a pretty neat wrapper that allows us to draw images dynamically based on other instances we have kept track of.
Check out this Codepen for a working example.
window.app = window.app || {};
app.Canvas = document.getElementById('myCanvas').getContext('2d');
app.Image = function(source, x, y) {
this.x = x;
this.y = y;
this.data = new Image();
this.data.addEventListener('load', this.draw.bind(this));
this.data.src = source;
};
app.Image.prototype.draw = function() {
app.Canvas.drawImage(this.data, this.x, this.y);
};
app.Image.prototype.getImageBounds = function() {
return {
height: this.data.height,
width: this.data.width
}
};
var myImage = new app.Image('http://placehold.it/250x250', 10, 10);
var mySecondImage = new app.Image('http://placesheen.com/100/100', myImage.x + 10, myImage.y + 10);
The most important line is the last one. Notice how we're initializing a new app.Image with x and y coordinates relative to the first image. By using a custom wrapper class that keeps track of this information, we're able to easily access the necessary data that we need in a variety of circumstances.
I hope this helps to get you on the right track! Let me know if you have any questions about the code, and I'll be glad to explain.
Related
I'm trying a basic display of a preloaded image with p5.js library (instantiation mode):
var sketch = function(p) {
var fondo;
p.preload = function() {
fondo = p.loadImage('app/themes/mrg/dist/images/tramas/example.jpg');
};
var viewportWidth = $(window).width();
p.setup = function(){
canvas = p.createCanvas(viewportWidth, 200);
canvas.background(255);
canvas.image(fondo, 0, 0);
};
};
new p5(sketch);
The canvas was created but no image is there.
Here is a working example:
https://stage.margenesdelarte.org/
The canvas is at the end of the page (with white background) but no image is rendered inside.
Image path is right, since there is no error in the console and it can be reached in its place:
https://stage.margenesdelarte.org/app/themes/mrg/dist/images/tramas/example.jpg
What is wrong, and how can I display this image? Thanks!
That's correct version? (I used BASE64 because I didn't want to run a local server)
var sketch = function(p) {
var fondo;
p.preload = function() {
fondo = p.loadImage("data:image/gif;base64,R0lGODdhMAAwAPAAAAAAAP///ywAAAAAMAAwAAAC8IyPqcvt3wCcDkiLc7C0qwyGHhSWpjQu5yqmCYsapyuvUUlvONmOZtfzgFzByTB10QgxOR0TqBQejhRNzOfkVJ+5YiUqrXF5Y5lKh/DeuNcP5yLWGsEbtLiOSpa/TPg7JpJHxyendzWTBfX0cxOnKPjgBzi4diinWGdkF8kjdfnycQZXZeYGejmJlZeGl9i2icVqaNVailT6F5iJ90m6mvuTS4OK05M0vDk0Q4XUtwvKOzrcd3iq9uisF81M1OIcR7lEewwcLp7tuNNkM3uNna3F2JQFo97Vriy/Xl4/f1cf5VWzXyym7PHhhx4dbgYKAAA7");
};
var viewportWidth = 500;
p.setup = function(){
var canvas = p.createCanvas(viewportWidth, 200);
canvas.image(fondo, 0, 0); // doesn't work
p.image(fondo, 0, 0); // works fine
console.log(p.image, canvas.image); //there are different functions
};
};
new p5(sketch);
https://codepen.io/anon/pen/yPENXx?editors=1111
Explanation:
Both p and canvas has a image function but there are different image functions. You have to use p.image(). I think canvas.image() is has some relations with https://p5js.org/reference/#/p5.Image, but that's only my assumptions.
Is your file being localhosted? For p5 to access local files such as images, it needs to be localhosted... I recommend apache
I'm developing a printing tool using HTML5 canvas. As a test, I've tried to draw an image and a rectangle on the canvas, and then copy it to a new window for printing, using the code below. But all I'm getting in the new window is a blank page.
<!DOCTYPE HTML>
<html>
<head>
</head>
<body>
<canvas id="pageCanvas"></canvas>
<script type="text/javascript">
var canvas = document.getElementById("pageCanvas");
canvas.height="700";
canvas.width="1000";
var ctx = canvas.getContext("2d");
var imageData="data:image/png;base64,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";
var imageObj = new Image();
imageObj.src = imageData;
imageObj.addEventListener("load", function() {
ctx.drawImage(imageObj, 50, 100,1000,600);
ctx.beginPath();
ctx.rect(100, 101, 200, 100);
ctx.lineWidth = 7;
ctx.strokeStyle = 'black';
ctx.stroke();
}, false);
var printWindow = window.open('');
printWindow.document.write('<html><BODY>');
printWindow.document.write('<center>');
printWindow.document.write('<img src="' + canvas.toDataURL()+'"/>');
printWindow.document.write('</center></body></html>');
printWindow.document.close();
printWindow.print();
</script>
</body>
</html>
Can you please guide me to overcome this issue?
You're opening the new window and trying to copy the content of the canvas onto it immediately after attaching the load event handler to the image, before the handler has actually had a chance to execute.
Just move all the JS code starting with the var printWindow = window.open(''); line inside the event handler, and it should work.
Oh, and please indent your code, especially if you expect anyone else to read it.
Addendum: If you want to wait until multiple images have loaded, the simplest way is to count the load events and call a function when all of them have fired, like this:
var imageURLs = [ ... image URLs here ... ];
var imageObjs = [];
var imagesLoaded = 0;
for (var i = 0; i < imageURLs.length; i++) {
var image = new Image();
image.addEventListener( "load", function() {
imagesLoaded++;
if (imagesLoaded == imageURLs.length) allImagesLoaded();
} );
image.src = imageURLs[i];
imageObjs.push(image);
}
function allImagesLoaded() {
// now do something with imageObjs
};
You could also get fancy and play with things like ES6 promises, but ultimately, the end result is the same.
See also:
Can I sync up multiple image onload calls?
Javascript - wait images to be loaded
I'm currently making a basic canvas based game and I currently have my characters sprite set to a specific image in the directory. on the outside of the canvas i have a couple other images (that are also saved in the directory) that I would like to be able to click on to change the sprite to the image clicked.
I have tried playing around with some onclick funtions but have not had any success.i tried playing around with
var Player = function(){
this.sprite = 'images/char-boy.png';
this.x = 300;
this.y = 550;
}
by changing it to something like
var Player = function(){
this.sprite = function char_select(){
var toon = document.getElementById(this);
return toon;
};
this.x = 300;
this.y = 550;
}
this is what the html looks like
<img src="images/char-boy.png" id="boy" onclick="char_select()">
I have never used jsfiddle but i copy and pasted what i have in real quick and came up with this.
https://jsfiddle.net/tibbs/u2pztuxj/
Your image's onclick attribute does nothing as your code is erroneous - the function name is sprite, not char_select. It also needs to be part of an instance of Player.
Try this: (you don't need an onclick attribute on the image now)
var myPlayer;
//Define Player object
var Player = function() {
this.sprite = 'path/to/image.png';
this.char_select = function(clicked_img) {
//Set sprite to clicked_img's src attribute
this.sprite = clicked_img.src;
};
this.x = 300;
this.y = 550;
}
window.onload = function() {
//Create a new player instance
myPlayer = new Player();
//Add click listener for the image(s)
document.getElementById('boy').addEventListener('click', function() {
//Call the char_select function with the clicked image as an parameter
myPlayer.char_select(this);
});
//Add more event listeners as required...
}
I'm attempting to make a very simple meme generator, whereby you select the image you want to add text onto using a drop down menu. I can successfully select the image I want and display it within the canvas, however when I change my selection, instead of changing the image it adds it over the first image.
I'd like to be able to chose the image, and if i change my mind it simply replaces the current image. Any suggestions you might have would be very welcome!
Here's my code:
window.onload = function init(){
var selector = document.getElementById('selector');
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var imageObj = new Image();
var imagesObj = {
"fry" : ['images/fry.jpg'],
"badluck" : ['images/badluck.jpg'],
"success" : ['images/success.jpg']
};
selector.addEventListener('change', function(){
imagesObj[selector.value].forEach(function(item){
imageObj.onload = function() {
context.drawImage(imageObj, 0, 0);
};
imageObj.src = item;
});
});
}
It looks like this did the trick:
context.clearRect(0, 0, 298, 350);
I'm learning javascript, so a coworker is having me do basic animation in the browser. I just finished my code, using the canvas element to display images to the screen, but nothing happens when I run the code. My debug statements don't get printed to the console, nor do any errors. Can anyone see a problem with my code?
<html>
<body>
<canvas id="console" width="600" height="600"></canvas>
<script type="text/javascript">
(function() {
console.log("at top of script");
var ballImage = new Image();
ballImage.src = "http://upload.wikimedia.org/wikipedia/en/e/ec/Soccer_ball.svg";
var time_stamp;
var balls[];
var BALL_COUNT = 2;
function requestAnimFrame (cb) {
function fallback (cb){
window.setTimeout(cb, 10);
}
var func = window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
fallback;
func (cb);
}
function update() {
var ts = Date.now();
var time_elapsed = ts - (time_stamp || ts);
time_stamp = ts;
canvas = document.getElementById("canvas");
// update ball positions and detect wall collisions
balls.forEach(function (ball){
canvas.clearRect( ball.xLocation, ball.yLocation, ball.scaleWidth, ball.scaleHeight );
ball.update(time_elapsed);
canvas.drawImage( ball.image, ball.xLocation, ball.yLocation, ball.scaleWidth, ball.scaleHeight );
});
}
function programRun() {
update();
requestAnimationFrame(programRun);
}
/*
CLASS: ball
*/
function Ball() {
// all the code and functions for the ball class....
}
ballImage.onload = function() {
// fill up the array containing the ball objects
for (var i = 0; i < BALL_COUNT; ++i){
balls.push (new Ball ("ball" + i));
}
// start running the program
programRun();
};
console.log("got to end of script");
}) ();
<script>
</body>
</html>
I'm almost certain it's some basic thing I messed up, because I didn't get any errors back from running the code. Any help is appreciated :)
This line caused it..
var balls[];
correct it by replacing it with:
var balls = [];
you should see the logs then.
Update:
I created a fiddle with the code above and revised some fragments of your code to conform to a version that may suit your needs in writing your own version of the ball animation.
The following are the problems that I saw in your code:
Of course the array declaration mentioned above var balls[]; to var balls = [];
Don't forget to declare variables with the var keyword. I changed
time_stamp = ts;
canvas = document.getElementById("canvas");
to
var time_stamp = ts;
var canvas = document.getElementById("canvas");
3. Your html code suggests that the ID of the canvas is id="console" but your javascript tries to get an element with id="canvas".
Changed
<canvas id="console" width="600" height="600"></canvas>
to
<canvas id="canvas" width="600" height="600"></canvas>
Inside your ball.each() iteration uses the canvas element to invoke methods that are supposed to be within the CanvasRenderingContext2D.
Add something after your var canvas declaration.
var ctx = canvas.getContext('2d');
use the ctx variable to manipulate the canvas itself. This should be your function update() definition.
function update() {
var ts = Date.now();
var time_elapsed = ts - (time_stamp || ts);
var time_stamp = ts;
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext('2d');
// update ball positions and detect wall collisions
balls.forEach(function (ball){
ctx.clearRect( ball.xLocation, ball.yLocation, ball.scaleWidth, ball.scaleHeight );
ball.update();
ctx.drawImage( ballImage, ball.xLocation, ball.yLocation, ball.scaleWidth, ball.scaleHeight );
});
}
UPDATE:
Always use var when declaring variables. If you want to use them as a variable that can be accessed from different scopes(inner scopes) then you can do it by declaring them a scope higher.
Something like this:
function BallAnimation() {
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
function updateBall() {
ctx.fillRect(.....);
...
}
function Ball() {
this.canvas = canvas;
}
}
In such a manner you can still obtain the reference of the variables that you want to share from other scopes. Read this article to know more why vars are important.